1. Field of the Invention
This invention relates to magnetic bubble domain modules and, more particularly, this invention relates to digital-to-analog conversion utilizing magnetic bubble storage memory techniques particularly adaptable for addressing large capacity bubble memories.
2. Prior Art
Conventionally, a bubble memory module utilizes bubble storage means formed of a selected type of propagate elements arranged in loops with transfer-in and transfer-out gates or ports located adjacent to each loop for transferring bubbles in or out of the loops. These loops, called storage loops, have bubbles continuously circulating therein in response to an in-plane rotating magnetic field, and are either transferred out of the storage loops, or replicated, and the bubble, or the replicated portion, is propagated by the in-plane rotating field through a magnetoresistive sensor, which relies on a change of resistance of magnetoresistive material, such as Permalloy, to detect the presence or absence of a bubble propagated thereunder and to generate a signal which is sensed by a read-out device. Such detectors are conventionally arranged in a bridge network in which one leg thereof comprises an active detector and another leg thereof comprises a dummy detector; the former being the detector under which bubbles are propagated and the other detector, while subject to the same in-plane rotating propagating field, is out of the bubble path and balances the system against noise. Typical examples of bridge networks utilizing magnetoresistive detector devices are shown in the U.S. Pat. No. 3,833,858 to Leinhard, et al. and in the U.S. Pat. No. 3,953,840 to Cutler, et al.
Also in the prior art are a number of patents involving bubble memory organizations having addressing schemes directed to improving access time to the data stored in the storage loops. Typical examples in the field of decoders are the U.S. Pat. Nos. 3,911,411 to George, 3,757,314 to Homma, et al., 3,760,386 to Quadri and 3,858,188 to Keefe. There are also patents in the field of bubble memory organizations directed to analog-to-digital conversion, such as the U.S. Pat. No. 3,803,591 to Watanable, et. al., and in the field of thin films (but not bubble memories) U.S. Pat. Nos. 3,372,387 to Tolman and 3,334,343 to Snyder show digital-to-analog conversion.
However, lacking in the prior art is the utilization of bubble memory techniques including the bridge type magnetoresistive sensors to form a digital-to-analog converter which also facilitates economical accessing of digital information in a short period of time.
Thus, it is a primary object of this invention to provide a digital-to-analog converter utilizing a magnetic bubble memory techniques.
A second object of this invention is to provide a digital-to-analog conversion technique in addressing or reading large capacity storage modules in a relatively short period of time which would be as short as one cycle of the propagating in-plane magnetic field.
A third object of the invention is to provide a means for obtaining binary weighted output utilizing magnetic bubble memory techniques and magnetoresistive sensors formed in a bridge network.
A fourth object of the present invention is to provide a bubble memory type converter utilizing magnetic memory type storage loops and bridge type magnetoresistive sensors, all producible on a single chip utilizing conventional masking techniques.